Method and apparatus for graveling wells



April 1940- E. DAVIS ET AL 8,573

METHOD AND APPARATUS FOR GRAVELING WELLS Filed March 29, 1938 FIG 1 2F|G.4. 42

48 22 so 1 Q i x I 52 2 EUGENE L. DAVIS HQWARD S. COLE,JR. W. EDWARDLARSON Patented Apr. 23, 1940 PATENT OFFICE 2,198,573 ME'rnon ANDAPPARATUS, FOR GRAVELING WELLS Eugene L. Davis, Long Beach, Calil'.,Howard S. Cole, Jr., Fort Worth, Tex., Wason Edward Larson, San Pedro,

and Norman 0. Wells,

Artesia, Calil'., assignors .to The Texas Company, New York, N. Y., acorporation of Delaware Application March 29, 1938, Serial No. 198,630

14 Claims.

This invention relates to a method and apparatus for completing wellsand more particularly to the gravel-packing of a well, i. e., theplacing of a bed of gravel or other granular ma.- terial in a well atthe place where oil or other fluid to be produced enters from thesurrounding formations. The principal object of the invention is toprovide a method and apparatus for placing the'gravel effectivelywithout danger to the well which might otherwise occur through thesticking of equipment in the well, the misplacing of the gravel, or forother reasons.

The advantages and benefits to be gained from placing a gravel wallaround the liner or screen of a well for eliminating'sand trouble, whenthe producing formations are known to cause trouble from sanding orsloughing, are now well known. The gravel reduces the infiltration ofsand into the liner by entrapping this sand in its intersticesand alsoprotects and supports the walls of the well during the producing of thewell.

When gravel-packing is conducted with the normal or direct circulationmethod, a fluid such as drilling mud is usually circulated down throughthe tubing to the bottom of the well and then upwardly through theannular space between the tubing and the casing. Gravel is added to thecirculating fluid and passes outwardly from the lower end of the tubingstring, usually through a ball check valve, and into the cavity or spaceprovided at the bottom of the well in the producing sands. The gravelfreely collects or bridges at the check valve and it is often necessaryto remove and then replace the tubing string in order to repack thewell.

Another method of gravel-packing which is frequently unsuccessfulcomprises first placing gravel in the hole and then dropping or forcingthe liner, usually provided with a chisel point, down through the gravelto the proper position in the producing zone. It is not always possibleto force the liner down to the desired point and to keep it centeredin.the hole and occasionally the liner becomes stuck in the gravel withconsequent added expense and time delay in completing the well.

In accordance with this invention, after the drilling operations havebeen completed, usually with the underreaming of the well cavity in theproducing zone, a partially slotted liner, the slotted portion of whichsubsequently serves as the well screen, is run into the hole on a stringof pipe or tubing. The tubing is attached to the inside of the liner bymeans of a safety or releasable joint at the lower end of the liner.

A properly conditioned carried fluid such as drilling mud is circulateddown through the annular space between the. tubing and the casing andthen upwardly through the tubing. Gravel is added to the drilling fluidand, upon reaching the well cavity, the drilling fluid passes into thetubing through slots in a perforated bull plug attached to the liner andthen upwardly to the surface. The gravel thus is deposited in the wellcavity around the slotted liner or screen and forms an effective pack.

Upon completion of the packing operations, the tubing is disconnectedfrom the liner at the releasable joint and removed from the well and apacker or adapter is then placed in the well so as to seal the spacebetween the upper end of the liner and the well casing. In order toprevent the drilling fluid and gravel from entering the top of theliner, a device attached to the tubing just above the top of the linerserves to divert mud and gravel downwardly around the sides of the'liner, and also serves to center the tubing within the liner and tomaintain this centering action throughout the operation of disconnectingthe tubing from the liner at the releasable joint. Means are alsoprovided for preventing the drilling fluid from Icy-passing the gravelby entering the liner through its upper slots and leaving through thelower slots, as well as for automatically closing the opening in thelower portion of the liner when the tubing is disconnected at thereleasable coupling or joint. The liner is provided'with means forpreventing its rotation While the tubing is being disconnected and alsowith means for centering it within the casing.

For a better understanding of the invention, reference may be had to theaccompanying drawing in which:

Figure 1 is a vertical elevation, partly in section, through a wellcavity showing one embodiment of the packing apparatus in position afterthe gravel has been placed but before the tubing has been removed;

Figure 2 is a side elevation of the lower end of the bull plug;

Figure 3 is a view taken on line 3-3 of Figure 1 looking in thedirection of thearrows;

Figure 4 is an enlarged sectional elevation showing a modification ofthe releasable cou- Dling;

Figure 5 is a sectional elevation showing another modification of thereleasable coupling, while :which the liner l8 and bull plug 22 areattached to and suspended from the string of tubing 42.

. Figures 6, 7, 8, 9 and 10 show, in spaced relation, parts of themodified coupling of Figure 5.

In Figure 1 is shown the lower portion of a well having a casing l8 andan enlarged cavity l2 formed by under-reaming the producing sands orformation 14. A rat hole" I! may be formed at the bottom of the cavityfor centering the liner. The casing is secured in the hole as by cementl8 in the usual manner. A liner l8 comprising a tube or pipe somewhatsmaller than the internal diameter of the-casing l8 and having a slottedor perforated portion forming a screen 28, has attached at its lower enda bull plug 22. The bull plug comprises a length of tubing or pipe ofsubstantially the same diameter as the liner I 8 and is providedthroughout its center portion with slots or perforations 24. The bullplug is secured to the lower end of the liner l8 as by welding at 25 andis provided at which is preferably welded into the liner and this platehas an opening 88 and an upwardly projecting box 88 provided withinternal left threads 48.

The plate 84 with its threaded box 88 forms one part of a releasablecoupling by means of hand The lower end 44 of the tubing string isprovided with a threaded projection 48 having left hand threads andadapted to be screwed. into the box 88.

In order to prevent the gravel from entering the upper end of the linerl8 a diverter plug or collar 48 is secured as by welding to the tubing42. This plug is provided with a lateral portion 58 adapted to cover theupper end of the liner, and

also with a downwardly extending enlarged portion 52 having a slidingflt within and adapted to substantially close the upper end of the linerwhile the coupling 88-44 is being disconnected.

The plug portion 52 also serves to center or rather to space the upperend of the liner l8 concentrically with the tubing 42. A plurality ofspacer guide members 54 are attached to the liner l8 and serve to spacethe same evenly from the casing l8. A swab 56 is preferably securedaround the tubing 42 below the plug 48 to prevent as far as possiblecirculating fluid from passing down into the liner l8. In order toprevent the carrier fluid or drilling mud from by-passing the gravel inthe cavity l2 by entering the liner through the upper slots 88 andleaving the screen portion of the liner through the lower slots, otherswab members 88 may be secured to the tubing and spaced at intervalsthroughout the length of the screen portion 28.

In the operation of the form of the invention thus far described, thebull plug 22 is first filled with gravel 29 and the slotted plate 88then placed in the upper end of the plug. The bull plug is attached asby welding to the lower end of the liner l8 and the liner then attachedto the lower end of the tubing 42 by means of the,

threaded connection 88-44. The swabs 58 and 88 are, ,of course, securedto the tubing before The bull plug" the connection 88-44 is made. Thediverter plug is welded to the tubing with the liner hung freely at thewell head. After assembling, the

device is lowered into the well on the tubing string until the bull plug22 reaches the bottom of the cavity l2 and passes into the rat hole IS.The plate 28 will prevent rotation of the liner when the tubing is to bedisconnected at the coupling 88-44. The carrier fluid, which may be adrilling mud of low viscosity in order to allow the gravel to drop outwhile at the same time being sufilciently viscous to hold the gravel andprevent it from bridging before it gets in place, is then circulateddown through the space between the tubing 42 and the casing Ill. Thefluid will enter the bull plug through the slots 24 and 28 and will passupwardly through the gravel therein and through the tubing 42 to thesurface. Gravel 8| is then added to the circulat ing fluid and passesdownwardly therewith until it reaches the cavity l2. The swabs 60 willprevent the fluid from by-passing the gravel which will be forced downto the bottom of the cavity,

whereupon the fluid will enter the bull plug, as I before stated,through the slots 24 and 28 and return to thesurface through the tubingstring. Gravel may be added to the circulating fluid continuously or itmay be added intermittently, the

circulating fluid serving to wash the gravel down to the cavity.

When about half of the gravel has been placed in the well it ispreferable that the mud be conditioned with some suitable chemical so asto reduce the gel strength so that it can then enter the tubing moreeasily. The remainder of the gravel is then circulated into the cavityby means of the conditioned mud until the cavity and prewhich may haveaccumulated at that point from entering the liner. The swab 58 will alsoaid in this respect. The tubing is then withdrawn from the hole and asuitable packer or adapter 82 lowered into position so as to seal thespace between the upper end of the liner l8 and the casing ill. The holeis then bailed so as to remove the water and the well is in conditionfor production.

It is possible that the velocity of the gravel carrying mud through theupper rows of slots 24 in the bull plug may tend to pack gravel at thispoint and leave an unpacked hole below. Again, the upper end of the holeI 5 may become bridged over with gravel due to the passing of the fluidthrough the upper slots 24 and into the tubing through the opening 88.In order to prevent future flow of sand from below such a bridge intothe liner, a somewhat modified form of releasable coupling is shown inFigure 4, in which the plate 84 is provided with a seat for a ball valve18 preferably formed of a phenolic condensation product such asBakelite. The threaded end 48 of the tubing is provided with a shortsleeve extension I2 which has a plurality of vertical slots 14 formedtherein. A plate I8 having a plurality of holes 18 is welded into theupper end of the bull plug and serves as a support for a compressionspring adapted to bias the ball valve IO upwardly toward its seat in theplate 34. Thus, when the threaded end 8 of the tubing is connected tothe threaded box 38, the circulating fluid will pass through the slots14 and upwardly through the tubing. However, upon unscrewing the end 46from the box 38, the ball valve 10 will be forced upwardly and willengage its seat in the plate 34 when the tubing is removed, thuspreventing further upward flow. In time the valve will become sanded inplace and deterioration of the spring 80 will have no effect upon itsaction.

Figures 5 and 6 show another modification of a device for preventingupward flow from the bull plug after the tubing has been removed. Athreaded plug 82 having the same pitch and lead as the threads of thejoint 38- is provided at its upper end with a lateral slot 84 adapted tobe engaged by a corresponding key 86 secured to the lower end of thethreaded extension 46. In the made-up position, slots 88 in the threadedplug 82 provide for circulation in either direction, but upon unscrewingthe connection 3l the key 86 causes the plug 82 to turn until the slots88 have passed upwardly within the plate 34. The key 86 will bedisengaged from its slot 84 on removing the tubing and circulationwill-thus be prevented.

It will be noted that in case it is desired to use normal or directcirculation during or after the gravel-packing operation, this may bedone since all of the forms as shown in Figures 1, 4 and 5 provide forcirculation in either direction.

As an alternative method of preventing the carrier fluid or drillingfluid from by-passing the gravel in the cavity If by entering the linerthrough the upper slots 58 and leaving the screen portion of the linerthrough the lower slots, the swabs 58 and 68 may be dispensed with, andthe annular space between the tubing and the liner may be filled with asoft, salve-like, water-insoluble material such as grease, other viscousfluids, or impermeable solids or semi-solids which would prevent thecirculating fluid from entering into the liner from its upper end andwhich, at the well temperature, would be sufficiently viscous so that itwould not pass outwardly through the slots in the liner. After thegravel packing operation has been completed, the material filling theliner can be removed by bailing, by circulating with suitable fluid, bybeing dissolved in a suitable solvent, or other, means.

A still other method of forcing the circulating fluid-to descend throughthe full length of the annular space between the formation and the linerconsists in placing inthe liner opposite the screen portion 20 a liningof cement, metal or other material which will close the liner slots andwhich can be subsequently drilled out after the gravel-packing operationis completed. In this case the left hand screw connection 38- may beplaced at the upper end of the liner l8 rather than at its lower endsince the operation will be the same after the lining has been drilledout.

Obviously many modifications and variations of the invention may be madewithout departing from the spirit and scope thereof, and there fore onlysuch limitations should be imposed as are indicated by the appendedclaims.

We claim:

1. Apparatus for gravel-packing a well comprising a string of pipeextending from the surface to a point near the bottom of the well, a

tube having a perforated screen section, said tube surrounding andspaced from the lower end of said pipe, a releasable connection betweenthe lower end of said pipe and a point in said tube below saidperforated section, a tubular 'extension closed at its lower end andconnected to and extending downwardly from the lower end of said screentube, said extension having perforations in its lower end and in itsside walls and adapted to be filled with a quantity of granularmaterial.

2. Apparatus for packing a well with granular material comprising aperforated liner tube, a tubular extension connected to and projectingdownwardly from the lower end of said liner tube, said extension beingclosed at its lower end and containing a quantity of granular material,said extension containing perforations through which liquid to beproduced can pass to the interior of said extension and means forlowering said liner tube into a well comprising a string of drill pipeand a releasable connection between the lower end of said pipe stringand the lower end of said liner tube.

3. Apparatus for packing a well with granular material comprising astring of pipe extending from the surface to a point near the bottom ofthe well, a perforated liner tube surrounding and spaced from the lowerportion of said pipe,

a releasable coupling between the lower end of said tube and thelowerend of said pipe string, said coupling including a left hand screwconnection, a perforated bull plug connected to and extending downwardlyfrom the lower end of said liner tube, said bull plug containing aquantity of granular material, and means attached to and projectinglaterally and downwardly from the lower end of said bull plug so as toengage the earth formation and prevent rotation of said bull plug andliner while said pipe string is being disconnected from said liner atsaid releasable coupling.

4. Apparatus for packing a well with granular material comprising aperforated tube adapted to be placed in the productive zone of a well, astring of pipe extending from the surface to a point near the bottom ofthe well, the lower portion of said pipe being within said tube, meansfor releasably coupling the lower end of said tube to the lower end ofsaid pipe including a threaded connection, a collar secured to said pipeand forming a tight cover for the upper end of said tube during thegraveling operation, said collar having an extension projectingdownwardly into the upper end of said tube so as to maintain the upperend of-said tube substantially closed while said coupling is beingunthreaded.

5. An assembly for use in placing gravel or like material in a well,comprising a string of pipe extending from the surface to anoil-producing zone, a tubular member having perforations therein andadapted to be placed in the well opposite said oil-producing zone andaround but spaced from the lower portion of said pipe, a releasablecoupling between the lower end of said pipe and said tubular member,said coupling containing an opening connecting the interior of the pipewith the space exterior of said tubular member, and a plug secured tosaid pipe for tightly covering the upper end of said tubular member, thearrangement being such that when circulating a carrier fluid containinggravel downwardly in the well around said pipe string, said plug willprevent the gravel and carrier fluid gravel will be deposited so as toform a filter bed around said tubular member.

6. An assembly for use in placing gravel or" like material in a well,comprising a string of pipeextending from the surface to anoil-producing zone, a tubular member having perforations therein andadapted to be placed in the well opposite said oil-producing zone andaround but spaced from the lower portion of said pipe, 2. releasablecoupling between the lower end of said pipe and said tubular member,said cou-' pling containing an opening connecting the interior of thepipe with the space exterior of said tubular member, a plug secured tosaid pipe for tightly covering the upper end of said tubular memberduring the graveling operation, the arrangement being such that whencirculating a carrier fluid containing gravel downwardly in the wellaround said pipe string, said plug will prevent the gravel and carrierfluid from entering said tubular member at its upper end, so that thecarrier fluid will enter said tubing through the opening in saidreleasable connection while said gravel will be deposited so as to forma fllter bed around said tubular member, and

means cooperating with said releasable coupling for closing the openingtherein when the pipe string is uncoupled from said tubular member.

'7. Apparatus for gravel-packing a well comprising a string of pipeextending from the surface to a point near the bottom of the well, aperforated screen tube surrounding andspaced from the lower portion ofsaid pipe, a releasable coupling between the lower end of said tube andthe lower end of said pipe string, said coupling including a left handscrew connection and an opening connecting the interior of said pipewith the exterior of said screen tube, and means for automaticallyclosing said opening when said coupling is disconnected, said meanscomprising a valve, means for biasing said valve toward said opening,and means on the lower end of said pipe for holding said valve away fromsaid opening while the screen tube and pipe are connected.

8., Apparatus for gravel-packing a well comprising a string of pipeextending from the surface to a point near the bottom of the well, aperforated screen tube surrounding and spaced from the lower portion ofsaid pipe, a releasable coupling between the lower end of said tube andthe lower end of said pipe string, said coupling including a left handscrew connection and an opening connecting the interior of said pipewith the exterior of said screen tube, and means for automaticallyclosing said opening when said coupling is disconnected, said meanscomprising a valve, means for biasing said valve toward said opening,and a slotted sleeve connected to and projecting downwardly from thelower end of said pipe, so as to hold said valve away from said openingwhile said coupling is made up.

9. Apparatus for packing a well with granular material having a casingand an enlarged cavity in the producing formation comprising a tubularmember provided with perforations to form a well screen, means forlowering said tubular member into said cavity comprising a string ofpipe, a releasable connection between the lower end of said pipe stringand said tubular member at a point below said screen portion, means forelos- 1 ing the space between said pipe and the upper end of saidtubular member while said releasable coupling is being disconnected, anda plurality of flexible packing members secured to said pipe andengaging the inner surface of the screen portion of the tubular memberso as to prevent the circulation of fluid longitudinally through saidtubular member while connected to said prising a string of pipe, areleasable connection between the lower end of said pipe string and saidtubular member at a point below said screen section, means foruncoupling said connection so as to remove said pipe string from thewell after the gravel-packing operation, and means for preventing graveland fluid from entering said tubular member through its upper end orthrough its perforations comprising a quantity of a soft, salve-like,water-insoluble material in the space between the pipe and the tubularmember which material at the well temperature is resistant todisplacement by the mud fluid and gravel but which is capable of beingremoved subsequently as by bailing.

11. Apparatus for gravel-packing a well having a .casing and an enlargedcavity in the producing formation below said casing, a tubular memberprovided with a perforated screen section, a pipe string on which saidtubular member is adapted to be lowered into said cavity, said tubularmember being larger in diameter than said pipe string but smaller thansaid casing so that annular spaces are provided between saidtubularmember and said casing and between said tubular member and saidpipe string, a releasable connection between the lower portion of saidtubular member and the lower end of said pipe string, means for closingthe upper end of the annular space between said tubular member and saidpipe string during the graveling operation and while said coupling isbeing disconnected, the arrangement being such that on circulatinggranular material and a carrier fluid into said cavity through theannular space between said tubular member and said casing, the carrierfluid will pass around the tubular member and will enter the lower endof the pipe string to pass upwardly to the surface through said pipestring while the granular material will remain in said cavity, andpacking means adapted to seal the annular space between said tubularmember and said casing after the gravel has been placed in said cavity.

12. The method of gravel-packing a well provided with a cavity in theproducing formation and a perforated tubular screen in said cavity andconnected to the surface by means of a string of pipe, which comprisescirculating granular material and a mud laden fluid downwardly into thewell to the cavity through the space between the screen and the walls ofthe well so that the fluid will enter said pipe string and return to thesurface while the granular material will remain in said cavity aroundthe screen, conditioning the mud fluid so as to reduce its gel strength13. The method of packing a well provided with a cavity in the producingformations and a tubular member having a periorated screen portion, saidmember being connected to the surface by means of a string of pipe,which comprises circulating granular material and a carrier fluid intothe well cavity through the space between the tubular member and thewalls of the well while preventing the carrier fluid from entering thepipe string through the screen portion of the tubular member, causingthe carrier fluid to enter the pipe string at a point remote from saidscreen portion so that the granular material will be deposited in saidcavity around the tubular memher, and then removing the pipe string fromthe well so that liquid to be produced can enter said tubular memberthrough said screen portion and pass upwardly to the surface.

14. The method of packing with granular material a well provided with acavity in the producing formation and a perforated tubular screen insaid cavity and connected to the surface by means of a string of pipe,which comprises circulating granular material and a mud laden fluiddownwardly into the well to the cavity through the space between thescreen and the walls of the well so that the fluid will enter said pipestring and return to the suriace while the granular material will remainin said cavity around the screen, discontinuing the circulation when thecavity is partially full of granular material, conditioning the mudfluid so as to reduce its gel strength, resuming the circulation ofgravel and the conditioned fluid until the cavity has been filled withthe granular material, displacing the mud fluid in the well with water,removing the pipe string from the well, sealing the space between theupper end of the screen and the wall of the well, and bailing the waterfrom the well.

EUGENE L. DAVIS. HOWARD s. COLE, JR. w. EDWARD LARSON. NORMAN c. wELLs.

